Symmetrical trough waveguide antenna array

ABSTRACT

A symmetrical trough waveguide antenna array is provided wherein a section of trough waveguide has spaced radiating mode conversion portions. Each of the radiating mode conversion portions includes a member of gyromagnetic material spaced between the center fin and one of the side walls of the trough waveguide and a member of dielectric material spaced between the center fin and the opposite side wall. When an appropriate DC magnetic field is applied to the gyromagnetic member, signals propagating in one direction along the trough waveguide are converted from the even to the odd mode and consequently radiation of some of the signals occurs at the spaced portions of the waveguide. The section of trough waveguide further includes phase shifter portions. Each of the phase shifting portions includes a pair of members of gyromagnetic material with one of the pair between the center fin and one side wall and the other of the pair between the center fin and the side wall opposite the one side wall. When appropriate DC magnetic field bias is applied to the pair of gyromagnetic members associated with the phase shifter portion, a difference in phase occurs between the spaced radiating mode converting elements.

llite Sites Patent Wen [ 51 Mar. 28, R972 [54] SYMMETRHCAL TROUGH WAVEGUIDE ANTENNA ARRAY 52 vs. (II ..343/772, 343/778, 343/787, 343/854, 333/21 R [51] Int. Cl. ..H0lq 13/00 ["58 Field of Search;

[56] References Cited UNITED STATES PATENTS 3,015,100 12/1961 Rotman ..343/772 Primary Examiner-Eli Lieberman Att0rneyEdward J. Norton [5 7] ABSTRACT A symmetrical trough waveguide antenna array is provided wherein a section of trough waveguide has spaced radiating mode conversion portions. Each of the radiating mode conversion portions includes a member of gyromagnetic material spaced between the center fin and one of the side walls of the trough waveguide and a member of dielectric material spaced between the center fin and the opposite side wall. When an appropriate DC magnetic field is applied to the gyromagnetic member, signals propagating in one direction along the trough waveguide are converted from the even to the odd mode and consequently radiation of some of the signals occurs at the spaced portions of the waveguide. The section of trough waveguide further includes phase shifter portions. Each of the phase shifting portions includes a pair of members of gyromagnetic material with one of the pair between the center tin and one side wall and the other of the pair between the center fin and the side wall opposite the one side wall. When appropriate DC magnetic field bias is applied to the pair of gyromagnetic members associated with the phase shifter portion, a difference in phase occurs between the spaced radiating mode converting elements.

9 Claims, 8 Drawing Figures SYMMETRICAL TROUGH WAVEGUIDE ANTENNA ARRAY This invention relates to antenna arrays and more particularly to electronically controllable antenna arrays.

At the present time considerable effort is being expended to develop microwave systems which operate at millimeter wavelengths. Transmission lines fabricated on dielectric substrates such as strip transmission lines and microstrip transmission lines suffer from high dielectric loss and the possibility of mode conversion and radiation unless their transverse or cross sectional dimensions are substantially less than one-half wavelength. Because the transverse dimensions of the lines are small due to the operating wavelength, dielectrically loading, which further shrinks these dimensions, becomes highly undesirable at high microwave or millimeter wavelength frequencies. H W V At millimeter wavelengths, therefore, precision hollow waveguides are more desirable than strip transmission lines from the standpoint of loss. However, conventional hollow waveguides do not lend themselves to batch fabrication techniques and do not readily lend themselves to coupling of circuit elelments to semiconductor diodes or ferrite elements to the waveguide structure.

In an effort to lower the cost and to provide a new type of transmission line and method of making such a line, the applicant in Ser. No. 850,862, filed Aug. 18, 1969, provides a unique type of transmission line made up of a formed block of dielectric material having a configuration so as to provide a surface which, when covered by conductive film, provides a form of transmission line heretofore known as symmetrical trough waveguide.

Antennas of the symmetrical trough waveguide type are known. Conversion from a conventional low loss waveguide to a radiating waveguide is accomplished by changing the mode of signal propagation from even to odd mode. Rotman, in US. Pat. No. 2,943,325 describes an antenna array using symmetrical trough waveguides wherein conversion from the symmetrical or even mode to the asymmetrical or odd mode is accomplished by mechanically changing the phase velocity of the propagating waves in one of the pair of symmetrical troughs. While this arrangement will provide an antenna array, it does not lend itself to either batch fabrication of the array, a low cost array structure or a fast switching array.

it is therefore an object of this invention to provide a structure which is low cost, lends itself to batch fabrication techniques, is small in dimension and one which will provide a phased array having fast acting, easily controlled electronic means to produce a changing radiation pattern and beam direction.

Briefly this and other objects of the present invention are provided by a symmetrical trough waveguide antenna array including a trough waveguide section having two conductively connected side wall plates extending parallel to each other, a third fin plate positioned between the two side wall plates and extending longitudinally parallel to the two conductively connected plates, a plurality of radiation exciting means, each comprising at least one member of gyromagnetic material positioned between the fin and one of the side walls and at least one other member of dielectric material positioned between the fin and the other side wall, the member of dielectric material having a dielectric constant and permeability the product of which is substantially equal to the product of dielectric constant and permeability of the gyromagnetic material for one direction of propagation of a wave through the waveguide section, and means for appropriately biasing the gyromagnetic material with a DC magnetic field to change the radiation pattern of the antenna array.

The above-mentioned invention will be better understood by reference to the following description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a perspective view of a symmetrical trough waveguide with means for controlling the radiating characteristics of said waveguide,

FIG. 2 is a cross sectional view of a trough waveguide with a representation of the electric field of the even mode in a dielectrically loaded trough waveguide,

FIG. 3 is a cross section of a trough waveguide with a representation of the electric field of the odd mode in a dielectrically loaded trough waveguide,

FIG. 4 is a cross sectional view of a trough waveguide having exponentially tapered side walls,

FIG. 5 is a sketch of an electronically scannable trough waveguide antenna array,

FIG. 6 is a sketch illustrating the radiating direction of the main lobe of a trough waveguide antenna relative to the waveguide,

FIG. 7 illustrates a cross section of a means for biasing the type of trough waveguide antenna illustrated in FIG. 1, and

FIG. 8 illustrates a cross section of a combined radiating mode converting element and a phase shifting element in accordance with another embodiment of the present invention.

Referring to FIG. 1, there is illustrated a perspective view of a symmetrical trough waveguide 11. The trough waveguide 11 is made up of conductive side walls 13 and 15, a conductive bottom wall 17 and a substantially shorter, centrally disposed conductive center wall or fin 19 extending from bottom wall 17 forming symmetrical troughs l6 and 18.

The characteristics of a symmetrical trough waveguide 11 are such that the cutoff wavelength depends upon electrical height of the center fin or wall 19. The cutoff wavelength is approximately that at which the fin 19 is a quarter wavelength long at the operating frequency from the base 17. The height of the side walls 13 and 15 above the center wall or fin 19 is made sufficiently high to prevent unwanted or uncontrolled radiation. Less than half of a wavelength spacing between the side walls 13 and 15 allows for operation of the waveguide over a band of frequencies. The spacing between the side walls should not exceed a half wavelength at the highest operating frequency of the band of frequencies. For example, if a trough waveguide were to operate within a frequency range of about 6 gI-Iz., the height of the side wall may be 1.60 cm., the center fin may be 1.143 cm. and spacing between the side wall and the center fin 0.254 cm. wide. Between the center wall or fin 19 and the outer wall 15 is located trough 16. In trough 16 is a slab 21 ofgyromagnetic" material G113 such as YIG (Yittium Iron Garnet) sold by Trans Tech of Gaithersburg, Maryland.

The term gyromagnetic" material refers to ferrimagnetic. ferromagnetic and antiferromagnetic materials, which materials exhibit a phenomenon associated with the motion of dipoles in these materials which in the presence of a DC magnetic field is similar in many respects to the classical gyroscope. These materials and their properties are discussed by Lax and Button in Chapters 1 through 6 in a book entitled Microwave Ferrites and Ferrimagnetics" a MeGraw-Hill publication.

A slab of dielectric material 23 is positioned in trough 18 between center fin 19 and outer wall 13. The dielectric slab may be a ceramic material such as Stycast [(-15 sold by Emerson and Cumming, Inc., Canton, Massachusetts. The slab 21 of gyromagnetic material has a given dielectric constant. The dielectric constant of the slab 23 is made approximately equal to that of the dielectric constant of the slab 21 to maintain the symmetry of the waveguide.

A DC magnetic biasing field is applied in the direction of arrow 27 to the gyromagnetic slab 21. This field may be supplied by an electromagnet or a permanent magnet or a toroidal type structure to be described later.

Coupling into and out of the symmetrical trough waveguide structure 11 may be provided by a pair of coaxial couplers, not shown, comprising a center conductor and an outer concentric cylindrical conductor to excite electromagnetic waves along the trough waveguide and to couple electromagnetic waves from the trough waveguide. In the case of a coaxial coupler the outer conductor is connected to the outer walls 13 and 15 and the center conductor is connected to the fin 19.

As an electromagnetic wave propagates in the direction of arrow 25, a magnetic field vector associated with the electromagnetic waves appears to rotate in space in a clockwise direction when viewing the waves along the direction of arrow 27. For signals being applied in the opposite direction, or the direction of arrow 26, the magnetic field vectors at points 22 and 24 appear when viewing along arrow 27 to rotate in space in a counterclockwise direction.

In accordance with an explanation of the theory of gyromagnetic materials, unpaired electron spins in a gyromagnetic material tend to have their axes of spin aligned with an externally applied magnetic field. Electron spins are phenomena associated with the individual electrons within the material. If the spin axes are momentarily deflected from alignment with the externally applied field, they will precess gyroscopically about the line of the externally applied magnetic field. This precession is in a clockwise direction when looking along the line of the applied field.

Referring to FIG. 1, if the gyromagnetic material is placed in a region of circular polarization of the wave propagated within a waveguide, the magnetic intensity of the wave energy may be rotated in the same sense or in the opposite sense of the precession of the magnetic moment of the electron spin. In the case where the wave energy is in the same direction as that of the precession of the magnetic moment, the wave energy will encounter an effective permeability of less than unity or negative permeability. In the case where the direction of propagation of the wave is opposite the direction of precession, greater than unity permeability or positive permeability is provided.

The positive permeability is relatively constant with changes in the DC magnetic field bias. The negative permeability however, changes rather drastically with changes in the DC magnetic field bias. Changes therefore in the magnetic field bias essentially cause changes in the propagation of signals in one direction only, and hence such a structure is a nonreciprocal (anisotropic) device.

As mentioned above, signals traveling in the direction of arrow 26 for a DC magnetic bias in the direction of arrow 27 see a positive permeability and signals traveling in the direction of arrow 25 see a negative permeability. If the gyromagnetic slab 21 of FIG. 1 is a biased by a sufficient external gyromagnetic field in the direction of arrow 27 so that the product of permeability and dielectric constant for signals traveling in the direction of arrows 25 and 26 is equal to the product of permeability and dielectric constant of the dielectric slab 23, the impedance presented to electromagnetic waves propagating along the trough waveguide are substantially identical and the field in the troughs I6 and 18 will appear balanced. The electromagnetic signals propagating in the waveguide will be in the symmetrical or bound even mode as shown in FIG. 2. The electric field in the even mode is located between the center fin and the side walls. The intensity of the electric field lines increases from the bottom wall, is maximum in the dielectrically loaded regions provided by slabs 21 and 23 and at the top of the center fin, and then exponentially decays toward the open side. The direction of the electric field in trough I6 is opposite that in trough 13.

Changes in the DC magnetic field bias from the given sufficient bias causes a substantial change in the negative permeability for signals traveling along trough 16 in the direction of arrow 25. This substantial change in the permeability in trough 16 causes an unbalanced condition due to the difference in phase retardation between troughs 16 and 18. This changed bias may be about 2,556 oersteds for the above described arrangement. When this unbalanced condition occurs, a degree of mode conversion of the signals occurs from the bound even or symmetrical mode to the radiating odd or asymmetrical mode illustrated in FIG. 3. Due to the finite height of the side walls and the effervescent nature of the odd mode, the odd mode signals tend to leak out radiation. This differential phase retardation of the signal waves to stimulate radiation of these propagated waves in the waveguide as described above is nonreciprocal, because as discussed previously changes in positive penneability are minimal with changes in the DC magnetic field.

The field configuration of the odd mode in the dielectrically loaded trough waveguide is similar to the 'IE mode in a dielectrically loaded parallel plane waveguide. The electric field rises from the bottom of the trough to a maximum and then decays exponentially toward the open top as illustrated in FIG. 3. The electric field extends above the center fin and is in the same direction in both troughs.

Improved impedance matching of the relatively low impedance waveguide to the antenna free space may be had by tapering the side walls exponentially as illustrated by the cross section of the trough waveguide illustrated in FIG. 4.

In FIG. I, the side walls, center fin and the bottom wall are of conductive material and act as a unitary structure. The trough structure may be provided by the parts joined together or may be constructed, as illustrated in Ser. No. 850,862 filed Aug. 18, 1969, of formed dielectric material having the shape of a trough waveguide with conductive material coating thereon.

Referring to FIG. 5, there is illustrated an antenna array system. The system includes a trough waveguide section 33 having side walls 35, 37, a bottom wall (not shown) and center fin 39 between the side walls forming troughs 36 and 38. Signals from a transmitter 41 are coupled between the center fin 39 and the side walls 35,37 at one end 43 of the trough waveguide section array system. Receive signals are coupled from the opposite end 415 of the waveguide section 33 to receiver 44.

The waveguide section 33 includes a plurality of radiating mode converting elements 49, 51, 53, 55 and 57 which are each serially spaced along the length of the trough waveguide 33 which elements upon given changes in the DC magnetic field applied thereto cause conversion of signals propagating in the bound even mode to the radiating odd mode and consequently providing radiation of signal energy at these spaced points along the waveguide. The waveguide section 33 further includes phase shifter elements 50, 52, 54 and 56 spaced along the length of waveguide 33 between each of the mode converting radiating elements 49, 51, 53, 55 and 57 providing nonreciprocal phase shift of signals traveling between each radiating mode converting element.

Each radiating mode converging element comprises a slab of gyromagnetic material such as ferrite in one trough 36 on one side of the center fin 39 and a slab of dielectric material having a dielectric constant approximately equal to that of the ferrite in trough 38 on the opposite side of the center fin 39. As described above in connection with FIG. 1, the dielectric slab has a dielectric constant so that the product of permeability of the dielectric slab and the dielectric constant equals the product of permeability and dielectric constant of the biased gyromagnetic slab. Mode converting element 49 is made up of gyromagnetic material slab 59 in trough 36 and dielectric slab 61 in trough 38. Likewise, elements 51, 53, 55 and 57, respectively are made up of the respective gyromagnetic slabs 63, 67, 71 and 75 positioned in trough 36 and the respective dielectric slabs 65, 69, 73 and 77 in trough 38.

Upon the application of a different DC magnetic field bias, indicated by arrow 76 in FIG. 5, to respective gyromagnetic slabs 59, 63, 67, 71 and 75 for electromagnetic signals propagating from the transmitter toward the receiver, power is converted from a bound symmetrical or even mode to the radiating asymmetrical odd mode resulting in radiated power.

It has been found that the percentage of the power radiated per unit length of such an antenna as shown in FIGS. 1 and 5 is a function of the applied DC magnetic field. By increasing or decreasing the DC magnetic field strength, the amount of power radiating from each radiating mode converting element of the trough waveguide may be raised or lowered.

The direction of the major lobe of the radiating pattern of each of the exciter sections is similar to that of leaky wave an tennas. Referring to FIG. 6, the direction of the major lobe indicated by arrow 85 of FIG. 6 extending from the top 88 of trough waveguide 86 is dependent upon the relationship c/v,,,,, where c is the velocity of light in free space and v, is the phase velocity of the guided wave in a trough waveguide. The cosine of the angle 6 between the plane 87 normal of the trough waveguide and the radiating direction 85 is equal to c/v,,,,.

The far field interference pattern resulting from each of the separate radiating elements excited by the biasing of the DC magnetic field can be changed by alternating the various bias levels applied to the gyromagnetic material slabs 59, 63, 67, 71 and 75. This biasing is provided by the radiation control magnetic means 81 which is capable of providing various DC magnetic field bias levels to the radiating mode converting elements 49, 51, 53, 55 and 57 as indicated by the levels A,, A A and A being applied to the gyromagnetic material slabs 59, 63, 67, 71 and 75 in trough 36 where A,, A A and A, are 7 "different DC magnetic biaslevels. i

Also, the direction and the radiation pattern of the major lobe or plurality lobes can be determined by phaser shifter control magnetic means 83 by varying the space relationship between the radiating mode converter elements 49, 51, 53, 55 and 57. The effective space or phase relationship between the radiating elements can be accomplished by providing phase shifters 50, 52, 54 and 56 inserted between each of the radiating mode converting elements shown in FIG. 5. Each of the differential phase shifter sections consists of a member of gyromagnetic material located in both troughs 36 and 38. Gyromagnetic members F1, F3, F5 and F7 are in trough 36, and gyromagnetic members F2, F4, F6 and F8 are in trough 38. The phase shift control magnetic means 83 provides sufficient DC magnetic field bias in the direction of arrow 76 to the gyromagnetic members F1, F2, F3, F4, F5, F6, F7 and F8. The phase shifter control magnetic means 83 is capable of providing various DC magnetic bias levels to the phase shifter elements to provide various changes in permeability and consequently different phase shifts as indicated by the different phase shifts of 0 6 6 and 6., in FIG. 5.

The radiation control magnetic means 81 may be comprised of a plurality of electromagnets with an electromagnet associated with each radiation and mode converting element and more particularly the gyromagnetic slabs 59, 63, 67, 71 and 75. These electromagnets are connected by separate wires to a variable DC current source. Selection of a given DC current level to a given electromagnet is dependent upon the desired radiation pattern. If it is desired, for example, that all radiating and mode converter elements 4 9, 51, 53 and 55 and 57 radiate equally for a given far field radiation pattern, the DC current level to all of the electromagnets would be equal. If, on the other hand, it is desired that the elements 49, 51,53, 55 and 57 are not to radiate equally but to have the center elements 51, 53 and 55 radiate more than the end elements 49 and 57 to obtain a given radiation pattern, then the DC current level to electromagnets associated with slabs 63, 67 and 71 would be higher, for example, than the DC current level to the electromagnets associated with slabs 59 and 75. Further, the pattern can be changed by having less effective radiating elements per length of the waveguide. The DC magnetic bias can be determined so that phase unbalance does not occur at locations where radiation is to be minimized. For a further discussion on the effects of changes of amplitude of the radiating elements and changes of the spacing between radiating elements to control far field patterns of antenna arrays, see Section 7.7 of Introduction to Radar Systems by Skolnik, a McGraw-Hill publication.

The phase shift control means 83 like that of the radiation control means 81 may consist of a plurality of electromagnets associated with each phase shifter element 50, 52, 54 and 56 to provide when select levels of DC electric current is applied thereto, selected amounts of DC magnetic bias and selected amounts of phase shift between the radiating and mode converting elements. Selection of given DC current level to a given electromagnet is dependent upon the desired angle of the main beam or beams. Also, since the pattern is also changed by the relative spacing between the radiating elements, changes in the phase shift between the element further changes the pattern. For a further description of how various difi'erences in phase between radiating elements affect beam steering and beamwidth control, see Section 7.7 of above cited book by Skolnik.

Since the system is nonreciprocal in nature, that is, signals are phase shifted in one direction only and mode conversion takes place for signals in one direction only. Signals at the transmitter 41 are coupled in the even mode along the trough waveguide 33. At the radiating mode converting elements 49, 51, 53, 55 and 57, selected portions of the transmitted signals are converted to the odd mode and are radiated out of the open side of the trough waveguide section. Due to the nonreciprocal nature of this mode conversion, radiation takes place for wave propagation only in one direction. The amount of radiation occurring along the section of waveguide is such that no original transmitter energy reaches the end 45 of the waveguide section 33. Due to the reciprocal nature of antenna device incoming signals at the open side of the waveguide are converted from the odd to even mode only for waves propagating toward receiver 44.

The phase shift control magnetic means 83 for the ferrite phase shifters may be provided by a toroidal structure instead of an electromagnet where a closed loop of magnetic insulator material such as ferrite has a latching wire passed through the center of the ferrite similar to that illustrated in FIG. 4 of Ser. No. 850,862, filed Aug. 18, 1969, for providing a latched differential phase shifter with a trough waveguide. The DC magnetic field bias for the single slab of gyromagnetic material for the mode converting radiating elements may be provided by an arrangement as illustrated in FIG. 7. Referring to FIG. 7, a cross section of a latched gyromagnetic trough waveguide radiation exciter element is illustrated wherein powders 94 of gyromagnetic material are mixed into portions of the dielectric body 92. The dielectric body 92 is formed as illustrated and is covered by conductive material to provide the center fin 91, side walls 93 and 95 and bottom walls 96 and 97. A closed magnetic loop of gyromagnetic material is formed by the powders in the area 94 of the body and by a gyromagnetic slab 99 in the trough 100. The dielectric counterpoise is provided by slab 102. A biasing wire 101 is placed through and along the loop of gyromagnetic material and when a pulse of DC current from a DC current source 98 is applied along the wire 101, a closed magnetic path is introduced in the material which, when the current is stopped, the remanent magnetization provides the required DC magnetic field bias across the gyromagnetic material slab 99. The radiating control magnetic means for sending the proper DC pulse to latch the ferrite material for the radiating excitation section or the phase shifter section may include a computer system coupled to a DC current source.

Referring to FIG. 8 there is shown an alternate approach to the array arrangement of FIG. 5. The trough waveguide includes exponentially tapered conductive side walls 111 and 113, a conductive bottom wall 115 and a centrally disposed conductive ridge or fin 117 substantially shorter than the side walls as discussed above in connection with FIG. 1. Between center fin 117 and side wall 113 are positioned two slabs 121 and 122 of gyromagnetic material one above the other. Between the side walls 111 and center fin 117 is positioned a dielectric slab 125 above a gyromagnetic slab 127. If the gyromagnetic material slabs 122 and 127 are of the same dielectric constant and slabs 121 and 125 have the same products of penneability and dielectric constant for a given magnetic bias in the direction of arrow 129, propagation of electromagnetic signals in the direction of arrow 133 or arrow 132 when applied is in the even or symmetrical mode. Upon the application of a DC magnetic field bias above the given bias, for example, in the direction of arrow 129, electromagnetic signals propagating into the paper (arrow 132) undergo a differential phase retardation due to the change in permeability of the slab 121 and conversion takes place from the bound even mode to the radiating odd mode. Also, when changes occur in this DC magnetic bias level across the slab 121, there is a change in the DC magnetic bias level across the gyromagnetic slabs 122 and 127. This change in the DC magnetic bias causes changes in the permeability and the amount of phase shift imparted to signals propagating in the even mode. This structure is therefore cabable of both causing radiation by mode conversion and of changing the phase shift between the radiating mode converting elements.

What is claimed is:

l. A trough waveguide antenna array comprising:

a trough waveguide section having longitudinally extending conductive side walls spaced by a longitudinally extending conductive bottom wall with a shorter conductive center fin symmetrically disposed between said side walls and extending from said bottom wall to form a first trough between the center fin and a side wall and a second trough between the center fin and the opposite side wall, said walls and spacing being arranged so that upon the application of electromagnetic signal waves to said section over a given range of frequencies said section is capable of supporting said signals in the even and odd modes,

means for coupling said electromagnetic signal waves into and out of said waveguide section,

a plurality of radiating mode converting elements, each of said radiating mode converting elements comprising at least one member of gyromagnetic material positioned in a portion of said first trough and at least one other member of dielectric material positioned in a portion of 30 said second trough adjacent to said member of gyromagnetic material, said member of gyromagnetic material and said member of dielectric material being arranged so that upon the application of an appropriate DC magnetic field of a first value to said radiating mode converting element said electromagnetic signal waves propagate along that portion of said section including said element in the even mode and upon the application of an appropriate DC magnetic field of a second value to said radiating mode converting element said electromagnetic waves propagate along that portion of said section including said element in the radiating odd mode,

control means for selectively providing said first and second values of said DC magnetic field to said plurality of radiating mode converting elements to provide a desired far field radiation pattern.

2. The combination claimed in claim 1 including means for controlling the phase of said signal between each of said radiating mode converting elements.

3. The combination claimed in claim 2 wherein said phase control means includes a plurality of phase shifting elements wherein each phase shifting element comprises a first and second member of gyromagnetic material with a first member positioned in a portion of said first trough and a second member in an adjacent portion of said second trough.

4. The combination claimed in claim 3 wherein said phase shifting means is spaced between each of said radiating mode converting elements. 7, ,7

5. The combination claimed in claim 3 wherein said first and second members of gyromagnetic material of each of said phase shifting means is spaced below the respective gyromagnetic and dielectric members of each of said radiating mode converting elements.

6. The combination claimed in claim 3 above wherein said phase control means includes means for providing selected values of DC magnetic bias to said members of gyromagnetic material of said phase shifting means to change the steering angle of said radiation pattern.

7. The combination claimed in claim 1 above wherein said side walls of said trough waveguide are exponentially tapered.

8. The combination claimed in claim 1 wherein said trough waveguide includes a dielectric body formed in a manner to cause one surface of said body to define the two side walls, the

ridge between said two side walls and with a thin film of conductive material covering said one surface defining the ridge,

the bottom wall and side walls.

9. The combination claimed in claim 8 wherein said dielectric body has portions below the region of said first trough to in cooperation with said member of gyromagnetic material of said radiating mode converter element, and said conductive film provide a closed magnetic flux path loop. 

1. A trough waveguide antenna array comprising: a trough waveguide section having longitudinally extending conductive side walls spaced by a longitudinally extending conductive bottom wall with a shorter conductive center fin symmetrically disposed between said side walls and extending from said bottom wall to form a first trough between the center fin and a side wall and a second trough between the center fin and the opposite side wall, said walls and spacing being arranged so that upon the application of electromagnetic signal waves to said section over a given range of frequencies said section is capable of supporting said signals in the even and odd modes, means for coupling said electromagnetic signal waves into and out of said waveguide section, a plurality of radiating mode converting elements, each of said radiating mode converting elements comprising at least one member of gyromagnetic material positioned in a portion of said first trough and at least one other member of dielectric material positioned in a portion of said second trough adjacent to said member of gyromagnetic material, said member of gyromagnetic material and said member of dielectric material being arranged so that upon the application of an appropriate DC magnetic field of a first value to said radiating mode converting element said electromagnetic signal waves propagate along that portion of said section including said element in the even mode and upon the application of an appropriate DC magnetic field of a second value to said radiating mode converting element said electromagnetic waves propagate along that portion of said section including said element in the radiating odd mode, control means for selectively providing said first and second values of said DC magnetic field to said plurality of radiating mode converting elements to provide a desired far field radiation pattern.
 2. The combination claimed in claim 1 including means for controlling the phase of said signal between each of said radiating mode converting elements.
 3. The combination claimed in claim 2 wherein said phase control means includes a plurality of phase shifting elements wherein each phase shifting element comprises a first and second member of gyromagnetic material with a first member positioned in a portion of said first trough and a second member in an adjacent portion of said second trough.
 4. The combination claimed in claim 3 wherein said phase shifting means is spaced between each of said radiating mode converting elements.
 5. The combination claimed in claim 3 wherein said first and second members of gyromagnetic material of each of said phase shifting means is spaced below the respective gyromagnetic and dielectric members of each of said radiating mode converting elements.
 6. The combination claimed in claim 3 above wherein said phase control means includes means for providing selected values of DC magnetic bias to said members of gyromagnetic material of said phase shifting means to change the steering angle of said radiation pattern.
 7. The combination claimed in claim 1 above wherein said side walls of said trough waveguide are exponentially tapered.
 8. The combination claimed in claim 1 wherein said trough waveguide includes a dielectric body formed in a manner to cause one surface of said body to define the two side walls, the ridge between said two side walls and with a thin film of conductive material covering said one surface defining the ridge, the bottom wall and side walls.
 9. The combination claimed in claim 8 wherein said dielectric body has portions below the region of said first trough to in cooperation with said member of gyromagnetic material of said radiating mode converter element, and said conductive film provide a closed magnetic flux path loop. 